/*
 * The MIT License (MIT)
 * 
 * Copyright (c) 2020 邓俊兴 (Deng Junxing)
 * Email : jesson3264@163.com
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 * the Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

#include "scl_stack.h"
#include <stdlib.h>

void stack_init(st_node_t* stack)
{
	stack->next = stack;
	stack->prev = stack;
}

st_node_t* stack_top(st_node_t* stack)
{
	if (!stack || (stack->next == stack))
		return NULL;
	return stack->next;
}

st_node_t* stack_pop(st_node_t* stack)
{
	st_node_t* ret = NULL;
	if (!stack || (stack->next == stack))
		return NULL;

	ret = stack->next;
	dl_node_remove(stack, stack->next->next);
	return ret;
}

void stack_push(st_node_t* stack, st_node_t* node)
{
	if (!stack)
		return ;
	dl_node_add(stack, stack->next, node);
}

int stack_empty(st_node_t* stack)
{
	return (stack->next == stack) ? 1 : 0;
}
